Non-invasive or in vivo interrogation of biological tissues with light waves is becoming increasingly important in medicine. Some of the techniques employed are diffuse-reflectance spectroscopy, fluorescence spectroscopy, imaging etc. In many of these cases, the targeted tissues are subsurface. For example, in non-invasive monitoring of blood glucose with reflectance spectroscopy, the targeted issue is the subsurface dermis where glucose-retaining vasculature and interstitial fluids reside. However, a substantial portion of the collected light originates from the superficial epidermis layer which not only yields no useful information but also interferes with the characterization of the dermis tissue. It is particularly obstructive because the optical properties of the epidermis is highly affected by pigmentation, hydration and temperature variation, all of which prevents an accurate determination of the blood glucose even with elaborated calibration schemes.
The disclosed in this application includes a method and its embodiments for the characterization of subsurface tissues by suppressing the collection of light from the superficial layer that the probing light encounters. The invented method and techniques can benefit a variety of optical characterization procedures in which the targeted tissue is subsurface, as in the case of non-invasive monitoring of blood glucose. Also disclosed in this application is a method of acquiring cross-sectional tissue images of biological tissues and other matters with improved imaging depth and clarity.